A common type of extrusion die for extruding plastic material as a tubular film has first and second body members which form an annular extrusion orifice. The plastic material is fed to the die from one or more extruders and passes into one or more spiral grooves in a surface of one of the body members adjacent the other body member. To obtain good quality film, the plastic material extruded should be as homogenous as possible and at substantially the same temperature throughout. U.S. Pat. No. 5,261,805 (Gates) issued Nov. 16, 1993 describes an extrusion die which overcomes these problems to some extent, but there is still a need for an improved die in this respect.
It is therefore an object of the invention to provide an extrusion die for extruding plastic material as a tubular film which provides extruded plastic material in an improved manner with respect to homogeneity and consistency of temperature.